Production of salts of carboxyalkyl cellulose



United StatesPatefif'o PRQDUCTION-"OF; SALTSEOF CARBOXYALKYL it ICELLULOSE r Adrianus' L. Ba i g; Deve nter, Netherlandsgand David T;Milne, Fredericksburg, Va., as'signors. to-An1erican ViscoseCorporation, Wilmington, D'el.', a corporation oiDelaware- V f No Dra inApplication April 17,1951; i Serial No.-221 ,514 s 1 90 mm; oi; ace-2321This invention relates toapro'cess for producing .pu'ri- 1.1 fi'ed saltsof. acidic; colloidal'materials and moreiparticularly to the productionoffpurified salts of acidic colloidal I materials, which aresubstantially fibrous or are lhighly; c'omminut'ed, without the use oforgani'c js'olven'ts fand withoutvthe formation ofsolutions, gels, doughm sesi 20 pastes, etc, The processof the present invention is applicableto the production of" purified salts 'offany' acidic colloidal material,suchias' alginic acid, carboxy alkyl cellulose, carboxyalkylhydroxyalkyl 'cellulose, et'c. For purposes of simplicity-of.descriptiomlhowever, the; invention will be. described as. it isapplicable tolthe production. ofipurified salts of carboxyalkylcellulose, it being. understood'that this is done merely for purposes ofillustration and the invention is not tobelimited; thereby but onlyinsofar as the sameinay'jbe limited in 30 the appended claims. e v p 1It is known to produce salts ofacidiccolloidal mat'erials, such ascellulosic materials; by washing'the'crude ganic solvents. For example,sodium carboxymethyl 1'35 cellulose is produced by treating alkali"cellulose with sodium, chloroacetate' and then washing thejcrude re 1action mass with aqueous methyl or: ethyl} alcohol to remove impurities,such as sodium chloride, sodiumglY- colate, and the like; A. product;purified'in thisfm anner 40 and dried, can be milledt'o a finely dividedfihrousieon-1 j' dition. However, a method. of this. type issubject; to.1 afnumber of disadvantages. The method is slow; and costly,particularly whenthecarboxyalkylationjis car ried-f out by the dough onkneader process in which 40 carboxyalkyl' cellulose-is' formed as ;,a-,compact, jdense dough or gel which is not easily penetrated by theaque-. ous organic wash liquor in additiomfthe recovery of the. organicsolvent, en'iployed' necessarily increases. the

complete so that the final product iscontaminated with by-product salts.

h also known 0 Produce saltsis fl acidic. 01151431} material, such ascellulose materials, by eut ralizingfthe; I

acid with alkalies .SLlChJfiS'. hydroxides: sodium, ammonium, potassium,fba'r if c.. neutralizations may be carried out, 'in the presencesufiicient water so thata solution. of theirjes'ulting" salt" is, formedor they may be carriediout without adding water, in which case, asthe."neutralizationjproceeds, doughy mass. is formed. The products soproduced-can be driedonly by such means as spreadingia thin layer onthesurface of-aheated drumor byjspray drying, e'tc. l

The rimary disadvantage ofgsuchaEpi-ocedurevis [that f the productsproduced; are not fibrous but, are hard, 5

horny, darkin color and difficult todissolve;

It is an object of this invention to overcome theidifli: eult-ies anddisadvantagesof-prior; art procedures-and. provide a method forproducing salts ofifacidicgcolloidal H material, such as cellulosicmaterials, iwhiclnia'r'elsubr' 7b tantially" jpu ze fibrousqand /oi::fineLy icommiuuted. with- .1, out resorting to the use of organicsolvents and without' any substantial reaction has taken, place .an ering thefl product into-a pasteorsolution, etc.- :5

. ventiomf. it ispossibletto elimin i ifi carhoxyalkyl;cellulos'eshaving at subf litu on,

z em l l he -hy x e ,"ca on s, or o od um; mmo um; m tin -ba um reactionmass with organic solventsor withia'queou's or Y terial f and? thef'salt-fortn ngzor neuti izi v ,as;tempeta ent q pm' n j e toisuitthe,particular product cf'orq the; conditions under;

ciallylffoig ydroigides which usually arevery'rea e. I Th t- 1 an re a es i h tth l rz1 snip ye suc ie b a es or ne su.ch. as; or, similar tiavailable; a a 121-11; the: casefof a canbi sa1t,,,;fo examplen theiz,"=stepsz' alkali cellulose, which hasbeentpnepaxzedciniconb ventionalmanner, i i

flitented lune-Zl 1195.551 1 Another object isto= provide a; new andfeconornical m h d 0 -P ZQ I JJE pl i i ncreme tia disi l colloidalmaterials andparticularly;Salts foficarboxyalkyl, celluloses.

'{Other objects and advantages-for the present inventionWillihegobviousfrom vthe descriptio "-ther'eoi hereinafiter.-, In; ge at ex i st .Q f henr s t inYen nar i ccom'plislied byforming-l.anyintimatemixture off the; i

V -acidic.colloidal naterialgjn;alwettcondition, foreiramp'le;carboxyalkyl cellulose, and aQsaltformingjj agDtuiider' conditions suchthat i-little or' sno reaction talgesgplace; F between them. Themixture, isthe'n comminuted before therea'ction is, caused to o rallowedto 5p ce .1n;t-f comminutedmass. In'thisway ,afinelydiyldedgproduis obtained which is substantiallyi free of; slumps ani orgelatinousgmaterialand which canibe; dried without; mam

Heret'ofore, it has been found-impractical, hsulistitu:

c-anboxyalkylgro on acomrrierci solvents. By employing Lthe. p eess ingwith organic solvents, andfjprepare p rifie 2.0. on more,carboxyalkyli'group' per-glucose u As a salt' forming or neutraligingagen th as s; h s-"qu t ma wammoniumt; The conditions -Of; {admixture oithe acid1 place. {The mixing of the I acid :ialiandj.the-salflforming,agent and comminutiojn of I ,thefmixlture ispreferably done. quiekly before substana, tially any} reaction; takeslace. Of courseythe, time al ot d 'td'm x naan commu ing-will.- vary. dpendi g p t ir ac i y o t p r cu a acidic colloidal materialzandthe'Ysalt-fo'rming agent being used; I 'In addition thefamountoiwater in the acidic colloidalma-Q ,teri lj gi q t t f The temperatureemployed-tor mix; 'ingtand'c o costs of, operation. Further,purification; is often in} '}the}salt for1ningagentfis.readilysolubildlji-fi waten es e5. 7

inuting is" preferably below that at Q or ing ase ty i ou l v. es- 0 v vah mmer millt of the n na' typ i L rotary, cutter, rotary" picker, etc,devices, withimqving" 'nventional s1}; for blowing a'ir;or;gases,}etc;';.Alternatively, the ,v ing 7 of the acidic colloidalmaterialiiandythelsalt-formingpr"2,

material and the neutralizing gen may be F performed :simultaneo itly.with. i --the comminution, depending,-ofieourse;on-thezequipment abaa-1at;amasaaattfia; e1 .oeesswcomprises 'fthegfollqwing y reactedwithia salt, of a, halogeno aliphatic acid with thorough mixing, such asin a device of the Werner-Pfleiderer type. The resultant reaction mass,comprising a salt of carboxyalkyl cellulose plus various impurities, isadded to an excess of an aqueous solution of a strong mineral acid, suchas sulfuric acid, and the like. The carboxyalkyl cellulose, beinginsoluble, is filtered olf and washed free of impurities with water. Theexcess liquor is then removed by centrifuging or by a suction filter,etc. and/ or by pressing, squeezing between rolls, etc. The carboxyalkylcellulose, which contains approximately 50 to 90% water, based on theweight of the damp mass, is then intimately mixed with a neutralizing orsalt-forming agent, such as hereinbefore named, under conditions suchthat substantially no reaction takes place, for example, at 20 C. for 5minutes in a mixer or shredder of the Werner-Pfleiderer type, or anyother conventional design. After thorough mixing, examination of theproduct shows it is still substantially insoluble in water.

The mixture of carboxyalkyl cellulose and salt-forming agent is thencomminuted in any one of the devices hereinbefore named. This is animportant step in the process. The product is comminuted to a fibrousand/ or finely divided state before any substantial reaction takes placeforming the water-soluble salt. By this process, purification iseifected Without a step which may form an undesirable solution, paste,gel, etc. resulting in the necessity of drying, as a result of which ahard, horny, and diflicultly soluble solid would be produced.

In order to effect reaction between the carboxyalkyl cellulose and thesalt-forming or neutralizing agent, sev eral procedures may be followed:(1) the comminuted mass may be stored for several hours at ordinarytemperatures, for example, for 8 to 24 hours at 20 to 30 C.; (2) thecomminuted mass may be heated to 40 to 60 C. for l to 3 hours; (3) thecomminuted mass may be dried at 60 to 120 C. in a rotary or tunneldrier, or in an oven, etc. The time of reaction varies generallyinversely with the temperature. In all three cases, a water-solubleproduct results which is fibrous and/orfinely divided and substantiallyfree of gelatinous material, and the like.

If desired, the purified and water-soluble salt of the carboxyalkylcellulose may be further comminuted, dried if necessary, and againcomminuted, or it may be processed by omission of any or all of thesesteps depending upon the nature of the product and/or its intended enduse.

The following examples are given to illustrate specific embodiments ofthe invention.

Example I A sodium carboxymethyl cellulose reaction mass, produced byreacting alkali cellulose with sodium chloroacetate in aWerner-Pfleiderer mixer and containing impurities, such as sodiumhydroxide, sodium chloride, sodium glycolate, etc., was added to anexcess of an aqueous sulfuric acid solution and thoroughly stirred. Thecarboxymethyl cellulose was filtered off and washed with warm wateruntil free of salts. The salt-free carboxymethyl cellulose was thencentrifuged until it contained approximately 60% water. Thecarboxymethyl cellulose had a degree of substitution of 0.9carboxymethyl groups per glucose unit. The carboxymethyl cellulose wasthen mixed in a Werner- Pfleiderer mixer for 5 minutes at C. withsuflicient sodium carbonate to neutralize it. The resultant mixture wasthen comminuted in a hammer mill while maintaining the temperature at 20C. The comminuted mass was then stored in cans at C. for a period of 16hours to allow the neutralization to take place. product was asubstantially pure water-soluble sodium carboxymethyl cellulose in afibrous condition substantially free of gelatinous material, and thelike, which could be dried without formation of lumpy, crusty, horny, ordiscolored material.

The resultant iug finely divided or fibrous salts of acidic colloidalma- 7 Example [1 Following the same procedure in Example I, a sodiumcarboxyethyl cellulose reaction mass was added to an excess of 15% H2804solution. The salt free carboxyethyl cellulose was centrifuged until itcontained approximately 70 water. The carboxyethyl cellulose was mixedwith sodium carbonate at 20 C. for 5 minutes as in Example I and thencomminuted in a hammer mill. The comminuted unreacted mass was thenheated to C. for 2 hours to eifect neutralization. The resultant productwas a pure water-soluble sodium carboxyethyl cellulose in a fibrous formwhich could be dried without becoming hard or discolored.

Example 111 The procedure of Example I was followed using hydroxyethylcellulose as a starting material and reacting the same with sodiumchloroacetate in the presence of caustic soda to form the sodiumcarboxymethyl hydroxyethyl cellulose. The acidic cellulose derivativewas centrifuged to 80% water content and then mixed with potassiumcarbonate, as in Example I, and comminuted in a hammer mill. Thecomminuted unreacted mass was then dried at 80 C. in an oven whereinneutralization took place. The resultant pure water-soluble potassiumcarboxymethyl hydroxyethyl cellulose was in a fibrous form.

Example IV A salt-free carboxymethyl cellulose, containing approximatelywater, was prepared as described in Example I. The carboxymethylcellulose was mixed in a Werner- Pfleiderer mixer for 5 minutes at l0 C.with sufficient sodium hydroxide to neutralize it. At this temperaturethe sodium hydroxide will not dissolve in the water present. The mixturewas comminuted in a hammer mill while maintaining the temperature at -l0C. Thereafter, the comminuted mass was stored under conditions such thatthe temperature thereof was allowed to rise slowly causingneutralization to take place. For example, the mass was allowed to standfor 16 hours while allowing the temperature to rise to 25 C. Thewater-soluble sodium carboxymethyl cellulose so produced was equal inquality to that produced in Example I.

Either sodium hydroxide and potassium hydroxide or both may be mixedwith the wet carboxyalkyl cellulose and the resultant mixture comminutedwithout reaction taking place by maintaining the temperature in a rangeof 5 C. to 20 C. or lower. In this range neither of the above-mentionedsalt-forming agents is soluble in water.

There are numerous advantages of the present proc-- ess among a few ofwhich are the possibility of producterials in substantially pure form,which are of desirable appearance, solubility, etc. without the use'oforganic solvents, i. e., without involving the expense of the solvents,their handling, recovery, etc. ent process permits the production ofvarious pure salts of acidic colloidalmaterials without the undesirableformation of pastes, gels, or solutions which are expensive anddifiicult to dry, and in addition, yield products, the appearance andother properties of which are inferior. The present process also permitsmanufacture of a wide variety of salts which is not possible when thereaction mass is washed with organic solvents. Further, it is possibleto produce mixed salts of acidic colloidal mate rials by means of thepresent invention, such as sodiumpotassium carboxymethyl cellulose, etc.

It is to be understood that the above description is merely illustrativeand that various changes may be made without departing from the spiritand scope of the invention as defined in the appended claims.

We claim:

1. A process for producing salts of a carboxyalkyl cel- Further, thepres lulose having a substitution of 0.6 to 2.0 carboxyalkyl. 7

groups per glucose unit comprising mixing the carl'ioxyalkyl cellulose,containing 50 to 90% water based on the weight of the wet mass, with analkaline-neutralizing agent at C. for a period of the order of5-rninutes,. the amount of said agent being approximately that requiredfor reactingwith the carboxyl groups of said cellulose, comminuting themixture before substantiallyany ingialkali entium with.sodiumchloroacetate, mixing "the reaction mass with arr-excess of anaqueous solution of sulfuric acid, filtering'flotf thecarboxymethylcellulose and 7 [Washing it with wateru'ntilfree of impurities,centrifug- I ing the 'carboxymethyl ;.eellulose untiliit jcontaius 60%,water, the amountao'f' sodium carbonate being approxi V ma'tely thatrequired for reacting with-the .carboxyl-gr'oups g of said cellulose;mixingthe,carboxymethyfcellulose-With.

neutralization takes place and then subjecting the com- .hours at C. toform a water-soluble sodium 'carboxy time varying generally inversely asthe temperature, tot

effect neutralization.

3. A process as defined in claim 2.wherein the coin- C. to allowneutralization to take place.

minuted mixture is stored for 8 to 24 hours-at 20 .to p

4. A process as defined in claim 2 wherein the comminuted mixture isheated to 40 to 6 0 for 1' to 3 hours to efiect neutralization. I

5. A process for producing water-soluble salts of car- I boxyalkylcellulose having a substitutionof 0.6 to-2.0

carboxyalkyl groups per glucose unit comprising reactof a strong mineralacid, filtering ofi thecarboxyalkyl cellulose and washing with wateruntil free of impurities, centrifuging the carboxyalkyl cellulose untilit con tains 90 to 50% water tmixing with a neutralizingagent' at 20 C.,the amount of said agent being-approximately boxymethylcellulose havinga subs titutionlof 0.610 2.0 carboxymethyl groups per glucose unitcomprisin'g .react- 'ingfallrali cellulose with :sodium'chloroa'ee'tate, 'mixing a the reaction mass with anlexcess of anaqueous solution] of sulfuric facidQfiltering. off the earboxymethyl'cellulose and washing it with water-until free of impurities, mixing 7sodium carbonateatZOjG',comminutingthelmixtureand H 7; then allowing thecomminuted mixtureto stand for 16 1 methyl cellulose inazfinely-dividedcondition. g

.8; A process for producing water-soluble salts I of cthe.*carboxymethyl cellulose with sodium hydroxide at a 5 temperaturelower than??? C.,; 'comminutin'g the mix ture at a'temperaturelowerl'thanf 5 ;c;,; n 1 then allowing the mixture'tostandatatemperaturebfabqut 25 C; for about; 16 j,hours' to form a sodiumcarboxytnethylfcel luloseina-finely divided condition; i I I .9.A-process 'forjproducingsalts, of a carboxyalkylicelel. lulose having agsub'stitution ofj ).6 tof2.0}'carboxyalkyl groups per glucose unit;comprising mixing thegearboxy-fi 'alkyl cellulosecontaining50to90% waterbased on the weight of t the wet jmasslwithalkaline neutralizing agent 5at 20.. C for aiperiod-on the order of 5 r r'iinutes;the :Q'

j amount of said agent being" approximately 'that frequired,

that required for reacting with the carboxyl groups of said cellulose,comminuting the mixture and then allowing neutralization to take placein the comminutedmixture to form the water-soluble carboxyalkylcellulose; salt to obtain a finely divided product. t i

6. A process as defined'in claim 5 wherein .the neutralizing agent isselected from the group consisting of in:

sulting in. a finely divided product.

organic hydroxides, carbonates, bicarbonate's, and quaternary ammoniumsalts. V t

7. A process ,for producing water-soluble salts of carboxymethylcellulose having a substitution of 0.6 to 2.0

carboxymethyl groups per glucose unit comprising reactfor react ngWith'the -carboxyl gr oups of'saideellulose,

.comminuting [the mixture substantially-beforeanyjneu- Y tralizing takesplace, then heating Ithefcornminuted lmix: ture at a temperature of to120-"C;unti1 dryqwitht 1 neutralization f taking place during saidheating and re- References Cited in the file of this patent :1 T D STA SIENTSY f 7 2,513,807 5 Lembem 1111M; 1950. 1 T N 572,868 v Great Britainet; 26.1945 I

1. A PROCESS FOR PRODUCING SALTS OF A CARBOXYALKYL CELLULOSE HAVING ASUBSTITUTION OF 0.6 TO 2.0 CARBOXYALKYL GROUPS PER GULCOSE UNITCOMPRISING MIXING THE CARBOXYALKYL CELLULOSE, CONTAINING 50 TO 90% WATERBASED ON THE WEIGHT OF THE WET MASS, WITH AN ALKALINE NEUTRALIZING AGENTAT 20* C. FOR A PERIOD OF THE ORDER OF 5 MINUTES THE AMOUNT OF SAIDAGENT BEING APPROXIMATELY THAT REQUIRED FOR REACTING WITH THE CARBOXYLGROUPS OF SAID CELLULOSE, COMMINUTING THE MIXTURE BEFORE SUBSTANTIALLYANY NEUTRALIZATION TAKES PLACE AND THEN SUBJECTING THE COMMINUTEDMIXTURE TTO CONDITIONS OF TEMPERATURE AND TIME WHICH CAUSENEUTRALIZATION TO TAKE PLACE TO OBTAIN A FINELY DIVIDED PRODUCT.